Direction finder



March 29, 1949. G s, BURROUGHS 2,465,350

DIRECTION FINDER March 29, 1949.

Filed May 2l, 1945 G. s. BuRouGl-ls 2,465,350

DIRECTION FINDER 2 Sheets-Sheet 2 BY /w Patented Mar. 29, 1949 ENCE DIRECTION FINDER Gordon S. Burroughs, Forest Hills, N. Y., assignor to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application May 21, 1945, Serial No. 594,861

14 Claims.

The present invention relates to direction iinders, particularly of the type utilizing cathode ray oscillograph tubes in the form of an inverted gure-of-eight or double-lobed pattern, in which the outer ends correspond to the nulls oi the radiant action pattern of the antenna system. If the null is not sharp, the outer ends of the lobed pattern become rounded and also tend to pull in away from the scale around the circumference of the screen thus making directional readings diiicult. Various other causes produce blurring or rounding of the outer ends of the lobed pattern or pulling away of said ends from the scale. Noise, for example, tends to mask the lobed pattern and frequently obscures the directional indication.

An object of the present invention is the pro- Vision of an improved direction finder giving improved directional indications.

Another object of the present invention is the provision of a direction finder in which the usual lobed or inverted gure-of-eight pattern on the screen of the cathode ray oscillograph tube is replaced by a straight line.

Another object of the present invention is the provision of an improved direction finder in which accurate directional indications are obtained despite a relatively high noise level.

A further object of the present invention is the provision of a direction finder in which thel pattern on the oscilloscope screen always has its outer ends or points on the edge of the screen adjacent the calibration so thatthe directional reading may be readily and accurately made.

Other and further objects of the present invention will become apparent and the invention Will be best understood from the following description of an embodiment thereof, reference being had to the drawings in which:

Fig. 1 is a block diagram of a direction finder embodying my invention;

Fig. 2 is a set of curves used in the explanation of the operation of the direction iinder of Fig. 1;

Fig. 3 is a modified embodiment of a direction nder embodying my invention; and

Fig. 4 is another modified form of a direction nder embodying my invention.

In systems of the type to which this application has reference, directive radiant action patterns are rotated and the circular sweep of a cathode ray oscillograph tube is rotated synchronously therewith. Energy picked up from a transmitter produces in the output of the direction iinding receiver a waveform similar to a full wave rectied sine wave having cusps repeated at a frequency twice the frequency of rotation of the radiant action patterns. In the prior art the output of the direction finding receiver is then applied to deecting means in the cathode ray tube to produce an inverted iigure-of-eight or double lobed pattern. In accordance with one aspect of my invention the cusps of the output of the D. F. receiver are sharpened to produce sharp pulses. These are applied to the deiiecting means to cause a thin line radial deflection of the circular trace and are also used to substantially simultaneously cause the unblocking of the cathode ray tube and thus light the screen. Consequently a thin line of light is produced on the screen indicating the line of direction. The foregoing and other aspects of my invention will become apparent from the following description of the embodiments thereof in which the same numeral is used for corresponding parts of all the ligures. Furthermore the curves in Fig. 2 and the other figures are not intended to have any exact quantitative significance, but are merely an aid in describing the operation of the systems mentioned herein.

Referring now to Fig. 1, a continuously shifting or rotating radiant action pattern in the form of a figure-of-eight is produced by means of a rotatable loop I adapted to rotate around a vertical axis 2 and driven by a driving means 3 as indicated by the broken line Li. The output of the loop l is applied to a direction finding receiver '5 whose output is in the shape of a full wave rectied sine wave as illustrated in curve A Fig. 2, the cusps of which correspond to the nulls of the iigure-of-eight pattern. Waveform A, a pulsing direct current, is fed by means of coupling condenser 6 to a peak clipper 1, the input to said clipper being in the form of an alternating current waveform B (Fig. 2). Peak clipper 1 cuts off the cusps or peaks of wave B at a high level, as indicated by broken line 8 (Fig. 2) and passes said peaks so that they appear in the output of the clipper in the form indicated in waveform C. that is, these peaks are inverted and amplified. The output of peak clipper l is fed to an amplifier 9 of the type which inverts Waveform C so that it appears ampliiied and inverted as in waveform D. The output of amplier 9 is alternating current which is fed to a direct current restorer I0 which adjusts the peaks of the pulse of waveform D to a level of Zero direct current potential with the troughs of said pulses being negative; as illustrated in waveform E. The output of the D. C. restorer l0 is then fed to the usual amplifier and inverter Il forming part of the cathode ray oscillograph equipment, which amplifier feeds the deiiecting coil I2 of a cathode ray oscillograph tube I3. The deflecting coil I2 is driven by the same driving means 3 which rotates thel antenna and is rotated synchronously with the rotation of said loop antenna I.

Amplifier I I is no-rmally conductive so that current normally flows through thedeecting coil I 2 and deflects'theaspotto the outer.circumference of the cathode ray tube screen. As the deflecting coil I3 is rotated the spot moves in a circle adjacent the outer circumference of the screen,. thus producing a circular trace.

When a signal, as in WaveformE, isimpressed upon the amplier I I, the spot'lwillgbe atfthe` outer circumference of the screenu-WhenIthe=peaks-of the pulses of said Waveform `are impressedy on amplifier II since these peaks are at zero voltage D. C. The troughs between said pu1sesfarenega tive and block conduction of the tube in amplifier .-I I, thus cuttingoff .the current iiow through de- .,lecting coil -I2 andpermitting thespot to move 'tothe center .of the Yscreen vand remain v.there .until the nextpeakvis-fencountere'd. This ,movement of the-spot fromthe outside ofsthefscreen to the center f produces a thin-lineV of.- light .onthe zscreen. 'Since the pulses -occur at an `interval AVcorrespmndingto half afrotationI of the .deflecting .,coil .around 4the tube,.tw o opposite andvfaligned .radial lines ,of light are; vproduced which indicate .the line of direction. IIhe foregoing assumes that .the cathode rayjoscillographtube I3 is conductive atfthe time-the sharp pulses-from D. C. restorer It are impressed upon amplifier Il. .The con- .ductivity of the-.cathode ray tube I3'is vcontrolled in the following mannertoeiect this result.

`Ii the cathode ray. tube were'zconductive all the time, noise interferencesawould .cause radial deflections of the circular.y trace and givefalse directional indications. Infaccordance withvmy invenltion, I provide an 'arrangement Whichcauses the cathode raytube 'I3 to light up only-forsa short .length of time duringwhich the pulses fare being impressed on the amplifier Il and-.theadeflecting coil :3. vFor-this purpose Iconnect the output of .ampilner 9 withgan amplifier -I5 Whichiisituned to a frequency equaleto twice -the-ffrequency iat which theloop--antenna Igisrotated. The;amplier- I5 may haveal.platefcircuitztunedfto,said frequency. The tunedcamplier-'Iggives an .output in WaveformfFiEig. 2,) ,in which the noise components have .been ,materially .reduced duetto the selectivity of the 1.amphi-ler. vTheoutputof tuned amplifier. I 5 is then fedy to. aI peakclipper :I 6

which clipsand passes the vpeaks thereof-above i a level El .indicatedinyvaveiorm .F y.to produce in itsoutput vv-aveform..G. r-Peak clipper |16 may be of a diode type or any other type-.which does not invert thevvaveform. Theoutput ofpeak clipper t6 is then fed toa limiter I-8 .which .limits` the amplitude o f=.theawaveaGtothe lever I6 of -Waveform G. .The outputof-limiter I8 isillustrated in Waveform H. -Since this -output is in theform ofalternating current, it-.vis thenfed to aDnC. restorer2il so that `the attops of said Waveform are at a zerodirect currentlevel; as in waveform I. The outputof the D. C..restorer-20.is theny impressed on thecontrol electrodeor grid -`2| .of the cathode ray oscillographftube I3.

As stated hereinbeforathe ,cathode ray tube I3 is normallyconductive. lAttthe yilat tops t2.2 oisaid Waveforml, thatzls, at zero D; C. potential, the screen of the .tube I3 will light. The troughs 2 3` of Waveform ,Lare however, sufficiently negative-.so y.as .to blankv out v-tube i3.

The pulses of Waveform E occur at approximately the middle of the fiat tops 22 of Waveform I. Thus cathode ray tube I3 will be lit at the time said pulses are impressed on deflecting coil I2 and consequently a thin radial line of light Will be produced on the screen of cathode ray tube I3. Because of the relatively greater w-idthiohtheat tops i22=go`f=waveform 'I in com- ,.pariso'n with'thenarrowness ofthel pulses of waveform E, if there is a shift in phase between the .rotation of loop antenna I and the tuned ampli- ,fier I.5 ,..the radial line of light Will still be visible 'on' the screen of the cathode tube i3. Modulation lasfwell.asznoiseyvill not yappear on the screen :between pulses .due to the blanking of the tube between said pulses.

Where, however, the arrangement is such that this phase shift is not likely to occur, an arrangement-.such as illustrated in Fig. 3 may be satisfactorily employed. In the embodiment of Fig. 3 @theloop antenna .I is `coupled to the .direction .zndingreceiver vFr-:Whose :output is then applied etotheftuned-.plate ampliiier l5. The tuned plate namplifier Ifi.substantially reduces the .noise and `qprodl-icesfa sine wave output .24 which is then Lclipped in.thepeak clipperlat a. high level.25 f-.andzthenpassed tothereby produce in theoutput offthe clipper -l6,..sharp.pulses-indicated by the ..;curve..26. -These sharp-alternating current pulses '26 arefapplied tothegrid- 2I ofk cathode ray tube -,I-3 to .brighten said tube,.vvhich is normally biased .tovcut-oii". Thepulses 2.6 are Ialso. used tofdeflect ,-thez-spotl--ai'ter theyhave been passed through-,5a Ll). C. restorerf-soithat the peaks thereof are at zero .potential as .indicated by .waveform .21. These pulses are applied to amplier II .Whose outputv is applied: to deflection coil I2as in Fig-.1.

:I'Ihe system ill-ustratedfin Fig. v3 has the advantage that the screen I3.is .only lit'vvhen the` pulses .arebeingapplied-.to.thedeflecting coil to deflect rthetrace. Thusrandominoisee-and other modu- .lation are i eliminated.

A :relatively `simple .systemis` illustrated in Fig. 4. In this system loop-.antenna I is coupled .to .direction I:finding .receivernf whoseoutput, .curve .28,fris then=.clipped.iii-peak.clipper .I6 above .the `level y2 9.of.curve. 28,toa pass the peaks and produce in its output a waveforml such .as illustrated ,in curve 30. .Thisoutput which .is` alternating cur- Arent-.is.thong-applied toa D. C. restorer IIJ topmriucepulses, curve .3 I, withtheir ,peaks at zero D. C.. level :and :troughs ...substantially negative, lfhese L.-pulses.;are then. applied-to .the `.grid .2 I .gf the cathoderaytube .-.I-3..to= control vthe illumina.-

' .tiontof its lscreen,-.sai d.tube.being normally conductive. The :pulses .of waveform 3l Vare 4also applied tosamplifier `I Ifwhose output is connected tothe :deiiecting ;coil.;I.2\a-nd. thereby controls .the deilection of thefspot inra manner-which-.willzbe understoodiromthe foregoing-description.

While I have describedithedetails ofwembodiments .-of..my invention, it rwill be apparent to thosefverse'dsin the fart L l,that numerous Jchanges may; be `@made -inrthesel details :without .departing from the teachings ithereof. For example, .fa sensing :arrangement .might be incorporated; in the equipment here .described in .a manner which will.beapparent=t-o thoseversed in theart. .Accordingly, while- Lhave described .above f the,prin c iplesofmy invention in. connection with specic apparatus, :and ,particular mod-ications thereof, it-isto be. .clearly understood ,that thisdescription is madefonlyby-.wayof example and notas a limi tation eon the scopefofmyinvention .as.dned.in theaccompanyingmaims.

claim:

1. In a direction finding system comprising a directional antenna device coupled to a direction finding receiver with means for cyclically shifting the directional pattern of said device, means for deriving from the output of said receiver a train of sharp pulses having a repetition frequency determined by the rate at which said directional pattern is shifted, means establishing the positive peaks of said pulses at zero direct current potential level, a cathode ray oscillograph tube, means for deflecting the beam of said tube from the center of the screen of said tube and rotating it in a circle, and means applying the train of established pulses to said deflecting means to control the deflection of the beam so that the beam moves radially during each of said pulses substantially in a line extending from said circle toward the center of the screen.

2. In a direction finding system comprising a directional antenna device coupled to a direction finding receiver with means for rotating the directional pattern of said device at a given frequency, means for deriving from the output of said receiver a train of sharp pulses having a repetition frequency equal to a low integral multiple of said given frequency, means establishing the positive peaks of said pulses at Zero direct current potential level, a cathode ray oscillograph tube, means for deiiecting the beam of said tube from the center of the screen and rotating it in a circle at a frequency directly related to said given frequency, and means applying the train of established pulses to said deecting means to control the deflection of the beam so that the beam moves radially during each of said pulses substantially in a line extending from said circle toward the center of the screen.

3. In a direction nding system comprising a directional antenna device coupled to a direction finding receiver with .means for rotating the directional pattern of said device at a given frequency, means for deriving from the output of said receiver a train of sharp pulses having a repetition frequency equal to twice said given frequency, means establishing the positive peaks of said pulses at zero direct current potential level, a cathode ray oscillograph tube, means deecting the beam of said tube from the center of the screen of said tube and rotating it in a circle at a frequency equal to said given frequency, and means applying the train of established pulses to said defiecting means to control the deflection of the beam so that the beam moves radially during each of said pulses substantially in a line extending from said circle toward the center of the screen.

4. In a direction finding system comprising a directional antenna device coupled to a direction finding receiver with means for rotating the directional pattern of said device, the output of said receiver being substantially in the form of a full wave rectied sine wave, means passing only the cusps o-f said receiver output to produce a train of sharp pulses each corresponding to one of said cusps, means establishing the positive peaks of said pulses at zero direct current potential level, a cathode ray oscillograph tube, means deecting the beam of said tube from the center of the screen of said tube and rotating it in a circle at a frequency directly related to said given frequency, and means applying the train of established pulses to said deflecting means to control the deiiection of the beam so that the beam moves radially at each of said pulses substantially in a line extending from said circle toward the center of the screen.

5. In a direction finding system comprising a directional antenna device coupled to a direction finding receiver with means for cyclically shifting the directional pattern of said device, means for deriving from the output of said receiver a train of sharp pulses having a repetition frequency determined by the rate at which said directional pattern is shifted, means establishing the positive peaks of said pulses at zero current potential level with the troughs between said pulses at a negative potential, a cathode ray oscillograph tube having a rotatable deflecting coil, means for rotating the deflecting coil at a speed related to said rate, an electron discharge device having a control element and normally conductive and providing in its output a direct current flow, means for applying said last named output to said deflecting coil, said direct current flow causing the deflection from the center of the screen of the beam which is rotated as the deflecting coil is rotated in a circle, and means applying the train of established pulses to said control element whereby the negative troughs inbetween said pulses diminish the conductivity of said electron discharge device so that the beam moves back toward the center of the screen inbetween said pulses and outwardly towards the circle during said pulses.

6. A direction finding system according to claim 1 further including means responsive to said sharp pulses controlling the conductivity of said cathode ray oscillograph tube.

7. A direction finding system according to claim 5 wherein said amplifier is tuned to a frequency equal to twice said given frequency and the repetition frequency is likewise equal to twice said given frequency.

8. In a direction finding system comprising a directional antenna device coupled to a direction finding receiver, with means for shifting the directional pattern of said device at a given frequency, means for deriving from the output of said receiver a train of sharp pulses having a repetition frequency equal to a low order integral rnultiple of the frequency at which said directional pattern is shifted, a direct current restorer, a cathode ray oscillograph tube, means deflecting the beam of said tube from the center of the screen of said tube and rotating it in a circle, means applying said sharp pulses through said direct current restorer to control the deflection of the beam, an amplier tuned to a frequency equal to the repetition frequency of said sharp pulses, means applying said sharp pulses to said tuned amplifier, the output of said amplier being in the form of a sine wave, and means responsive to the output of said amplier controlling the conductivity of said cathode ray tube.

9. In a direction finding system comprising a directional antenna device coupled to a direction finding receiver with means for cyclically shifting the directional pattern of said device, the output of said receiver being substantially in the form of a full Wave rectified sine wave, the cusps of which have a repetition frequency equal to a low order integral multiple of the frequency at which the directional pattern is shifted, an amplifier having its input connected to the output of said direction finding receiver, said amplifier being tuned to a frequency equal to said repetition frequency and providing at its output energy in the form of a sine wave, means for dewriving from the'ioutput of said' amplier a-Ltrain of pulses, said pulses corresponding to one :set .of

`peaks of said sine Wave, a cathode `ray oscillo- 4graph tube having a deiiecting element and a contro'l electrode, means for applyingk Asaid vsharp .pulses to said control electrode,y adirectcurrent restorer establishing the positivepeaks of said .pulses at zero direct current potential level also having said train of v.pulses vapplied to its input,

andmeansvfor applying the output .of -saidf direct -current restorer to saidk deiiecting 'elementto control the deilectionfof the beam of's'aid cathode ray tube.

110; In a direction findingv system comprising a directional device coupled` to a direction ndt,`

ing receiver with means for cyclically shifting the directional pattern of said device at a given frequency, means for deriving from the output .of

said receiver a train of sharp 'pulses having 'a repetition frequency equal to a low order inteygral multiple of said given frequency, means establishing the positive peaks of said pulses at yzero direct current potential level, a cathode ray `oscillograph tube having a control electrode. and deilecting means, and means applying the train of established pulses to said deflecting means and to said control electrode to substantially Isirnultaneously control the deflection of the beam and the conductivity of said cathode ray oscillograph tube.

11. In a direction nding system comprising a directional antenna device coupled to a direc'- tion finding receiver with means-for cyclically shifting the directional pattern of `said device, a.

cathode ray oscillograph tube, means cooperating with the said shifting means' for moving the tube ray trace in a circular path on the tube screen, means responsive to the output energy from the receiver to produce a wave having sharp cusps of energy to deflect the ray trace linearly bel tween said path and the screen center in accordance with the directional pattern,y means' noi' mally maintaining said tube conductive whereby rsaid linear deflection produce radial tracers and erating with the said shifting means for moving -the tube ray trace in a circular .path on the tube screen, Vmeans vresponsive to the output yenergy from the receiver .and operating independently of the amplitude variations of said energy to de- `iiect the ray trace linearly between said path and ,the screen center in accordance with the directional pattern, means normally maintaining said tube conductive whereby said linear deiiection produce radial tracers, means for blocking said tube between said deflection, and means for converting theroutput energy from the receiver into sharp 'pulses' for` coxitrollingv the ray deflectizrg means.

13. In a system as set `forth in `claimv 5 wherein .saidmean's vfor applying the train of established pulses comprises .an amplier tuned 4to a 'trenquency equal toa low order integral multiple of said rate, and means for applying energy from saidv tuned amplifier to control the conductivity :of said tube.v

V14.'. In a direction finding system comprising a directional antenna device coupled to a direcv.tion nding receiver',.means for cyclically shi-fting'the directional pattern of said device, a cathode ray oscillogra'ph tube, means cooperating vwith saidv shifting means and independent of said receiver output for moving the tube ray trace in a circular path on the tube screen, pulse Ishaping means responsive to the output energy .from saidv receiver and operating independently vof the amplitude variation oi said energy to` produce pulse energy for deilecting saidl ray trace linearly between said path and the screen center .in accordance Awith saiddirectional pattern, and means synchronized with said pulse energy for .blocking said tube between said 'deiiection GORDON S. BURROUGHS.

REFERENCES CITED' The following references are of record in the 'leof this patent:

UNITED STATES PATENTS Number Name A Date '2,263,377 yBusignies Nov'. 18, 1941 2,272,607 Higonnet Feb. 10, 1942 21,388,262 Ganiayre et al Nov. 6, 1945 FOREIGN PATENTS Number Country Date 635,793 Germany Y Sept. 28, 1936 

